Print details of Switchport in log
Print details of Switchport in log

__repr__ has been customized in base class, so using it can help to
print details of Switchport in log. Or else, only class name will be
printed, which is barely helpful.

Change-Id: I98bf878af6238d96cb2e48c29cd305883d4e7530

openstack/dragonflow,openstack/dragonflow,openstack/dragonflow